I’ve been reading Dan Linehan’s book, “SpaceShipOne: An Illustrated History.” It has some interesting history about the development of SpaceShipOne’s engine that seems to shed some light on the delays that Scaled Composites is having in developing the follow-on SpaceShipTwo vehicle.

The book recounts how Poway, Calif.-based SpaceDev won a competition against Environmental Aerospace Corporation of Miami to build SpaceShipOne’s engine. SpaceDev’s engine was lighter, performed better and was cheaper than the alternative. The company worked on the project from 2001 until 2004, when SpaceShipOne was retired after winning the Ansari X Prize.

However, the company did not continue to work with Scaled Composites on SpaceShipTwo, which is being built for Richard Branson’s Virgin Galactic company. Scaled decided to build the engine in house. This was reportedly due to sharp disagreements between spaceship designer Burt Rutan and SpaceDev founder Jim Benson.

Engine development was set back by a fatal explosion in July 2007 at the Scaled Composites facility in Mojave, Calif. The explosion killed three employees and injured three others. It also halted work on SpaceShipTwo for at least a year, according to Rutan.

In mid-August 2008, SpaceDev announced that it had teamed up again with Scaled. SpaceDev’s press release outlining the scope of the work:

Under the contract, SpaceDev will be the lead rocket motor team member for SpaceShipTwo and will collaborate with Scaledâ€™s internal design team to develop a production ready hybrid rocket motor. The SpaceDev teaming will be similar to that done from 2001 through 2004 on the SpaceShipOne program, in that SpaceDev will be providing engineering services to refine the design of the hybrid rocket motor being developed by Scaled Composites, as well as providing the development, manufacture and integration of key rocket motor system components.

Also, SpaceDev will again be conducting ground tests on those motor components and will be working to assist Scaled in the full-scale rocket test program both on the ground and during SpaceShipTwo flight tests. The contract, which runs through 2012, has an initial value of approximately $15 million for work to be primarily completed over the next two years.

For Scaled to bring in a new “lead rocket motor team member” more than three years into the development process is quite significant. It demonstrates the difficulties that Scaled has experienced in developing the larger engine and the seriousness of the explosion. And it helps explain why the schedule for commercial flights keeps slipping.